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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
CIS injector flow limitations?

Some of us have been debating if the injector is a limitation to how much fuel we can deliver.

I tend to believe they are not.

With EFI injectors, gross flow is determined at the injector based on injector size (20, 30, 55lbs...), fuel pressure, and how long the injector is open (duty cycle).

With CIS flow is determined by the CIS fuel distribution head. The upper lower pressure differential acting on the diaphragm and springs, the system-pressure level, and the internal orifice size -- mostly being what determines our gross fuel delivery capacity.

So, as long as the injector orifice is not smaller than the heads internal orifice, I would not expect a larger injector to be a source of increasing gross fuel delivery.

However, my "theory" is not enough to convince even me. What we need to do is some type of test.

What would this look like.

Maybe test a fuel head on an injector bench with the metering pin at the max delivery position without an injector.

Then to test a CIS injector at the same pressure and make a comparison.

I might suggest a pressure just under the system pressure regulator level to take that out of the equation and ensure the head orfice and injector see the same pressure.

What do we think?
Old 01-04-2010, 10:10 AM
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